Limitations of contrast enhancement for infrared target identification

Todd W. Du Bosq; Jonathan D. Fanning

doi:10.1117/12.817061

22 April 2009 Limitations of contrast enhancement for infrared target identification

Proceedings Volume 7300, Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XX; 73000G (2009) https://doi.org/10.1117/12.817061
Event: SPIE Defense, Security, and Sensing, 2009, Orlando, Florida, United States

Abstract

Contrast enhancement and dynamic range compression are currently being used to improve the performance of infrared imagers by increasing the contrast between the target and the scene content. Automatic contrast enhancement techniques do not always achieve this improvement. In some cases, the contrast can increase to a level of target saturation. This paper assesses the range-performance effects of contrast enhancement for target identification as a function of image saturation. Human perception experiments were performed to determine field performance using contrast enhancement on the U.S. Army RDECOM CERDEC NVESD standard military eight target set using an un-cooled LWIR camera. The experiments compare the identification performance of observers viewing contrast enhancement processed images at various levels of saturation. Contrast enhancement is modeled in the U.S. Army thermal target acquisition model (NVThermIP) by changing the scene contrast temperature. The model predicts improved performance based on any improved target contrast, regardless of specific feature saturation or enhancement. The measured results follow the predicted performance based on the target task difficulty metric used in NVThermIP for the non-saturated cases. The saturated images reduce the information contained in the target and performance suffers. The model treats the contrast of the target as uniform over spatial frequency. As the contrast is enhanced, the model assumes that the contrast is enhanced uniformly over the spatial frequencies. After saturation, the spatial cues that differentiate one tank from another are located in a limited band of spatial frequencies. A frequency dependent treatment of target contrast is needed to predict performance of over-processed images.

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Todd W. Du Bosq and Jonathan D. Fanning "Limitations of contrast enhancement for infrared target identification", Proc. SPIE 7300, Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XX, 73000G (22 April 2009); https://doi.org/10.1117/12.817061

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KEYWORDS

Image processing

Image enhancement

Performance modeling

Image contrast enhancement

Modulation transfer functions

Target recognition

NVThermIP

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